IB Computer Science HL

TechSolutions Inc. is expanding its R&D department and has recently configured a new internal network segment. The network administrator has provided a snapshot of the primary router's routing table (Figure 1) and a workstation's ARP cache within this new segment (Figure 2).

(a) Using Figure 1, identify the IP address of the default gateway for traffic leaving the R&D network.

Also, identify the network interface used by the router to reach the 192.168.50.0/24 subnet. [2]

(b) A workstation with IP address 192.168.45.10 needs to send a packet to a server at 10.0.1.75. Using Figure 1, deduce the IP address of the next hop gateway for this packet. Justify your answer. [3]

(c) Outline the process by which a router, upon receiving a packet, determines the next hop based on its routing table. [3]

(d) Discuss the purpose and necessity of both a routing table (Figure 1) and an ARP cache (Figure 2) in facilitating communication across a Local Area Network (LAN) and to external networks. [5]

MechPro Robotics is designing a new automated assembly line for manufacturing heavy machinery. A critical safety interlock system is being developed to prevent machinery operation if a human worker is detected within a hazardous zone. This system uses various sensors and actuators controlled by an embedded system.

Figure 1 shows a simplified logic circuit representing a component of the safety interlock. Input A represents an 'enable signal', Input B represents a 'safety guard closed' sensor, and Input C represents an 'emergency override' signal. Output Q represents a signal to enable machinery operation (Q=1 allows operation).

(a) Identify the type of logic gate labelled 'G1' in Figure 1. [1]

(b) Construct a truth table for the entire circuit shown in Figure 1, with inputs A, B, C and the final output Q. [4]

(c) Outline two reasons why an embedded system, rather than a general-purpose computer, would be a suitable choice for managing the real-time sensor data and actuator control in MechPro Robotics' safety system. [2]

(d) Explain how the operating system on an embedded system would manage an interrupt generated by Input C (emergency override) to potentially alter machinery operation. [3]

(e) The safety system needs to represent the distance of a worker from a piece of machinery using a fixed-point binary representation. Discuss the challenges and benefits of using fixed-point binary for this purpose. [5]

Synaptic Solutions is developing an embedded system for monitoring critical infrastructure, specifically a network of smart flood sensors deployed along riverbanks. Each sensor periodically transmits a 12-bit binary reading representing the water level. A central processing unit (CPU) running a real-time operating system (RTOS) processes these readings. The system also includes a safety module that triggers an alert based on multiple inputs.

Figure 1 shows the logic circuit for a crucial part of the safety module, which determines when to trigger an ALERT. The inputs are H (High water level - above threshold), R (Rapid increase in water level), and M (Manual override active - prevents alert).

(a) State the minimum number of bits required to represent a water level reading if the sensor range was extended to 0 to 4095. [1]

(b) Outline two roles of the Real-Time Operating System (RTOS) in ensuring the timely processing of sensor readings and critical alerts in this embedded system. [2]

(c) Refer to Figure 1.

(i) Complete the truth table in Figure 2 for the ALERT output of the logic circuit. [4]

(ii) Explain one reason why a hardware-based logic circuit, as shown in Figure 1, might be preferred over a software-based if-statement for this critical safety function. [2]

(d) The sensor data for water level is stored using fixed-point representation to improve accuracy for precise measurements. Discuss the advantages and disadvantages of using fixed-point representation compared to floating-point representation for this application. [5]

RoboSafe Systems is developing an embedded control unit for a new industrial robot arm, designed to prevent collisions in a hazardous manufacturing environment. The unit incorporates several safety sensors and logic circuits to process critical inputs. Figure 1 shows a simplified logic circuit used within the robot's control unit.

(a) Identify the type of logic gate labelled G1 in Figure 1. [1]

(b) Construct a truth table for the entire circuit shown in Figure 1. Your truth table should include columns for inputs A, B, C, intermediate outputs P1 and P2, and final output Q. [4]

(c) The robot arm's control unit uses registers like the Program Counter (PC) and Memory Data Register (MDR). Explain the primary role of the Program Counter (PC) within the CPU's fetch-execute cycle. [3]

(d) The robot's proximity sensors produce raw analogue data that needs to be converted and stored as digital values for processing. Discuss the implications of choosing between fixed-point and floating-point data representation for storing this sensor data in a safety-critical embedded system like the robot arm's control unit. [5]

OmniCorp operates a corporate network across several departments. A central router manages traffic between these subnets and the wider internet. The network administrator is troubleshooting an issue where devices in the 'Marketing' department cannot access a specific internal server. Figure 1 shows a simplified version of the router's routing table.

(a) State the purpose of the 'Gateway (Next Hop)' column in Figure 1. [1]

(b) A packet arrives at the router, destined for the IP address 192.168.20.45. Outline the steps the router will take to forward this packet based on Figure 1. [3]

(c) A network device with the IP address 192.168.30.150 attempts to send a packet through the router.

(i) Identify the 'Destination Network' entry from Figure 1 that the router will choose for this packet. [1]

(ii) Explain the rule the router applies to select this specific entry from the multiple matching routes in Figure 1. [3]

(d) OmniCorp plans to introduce a new server farm in a separate network segment, 192.168.40.0/24, directly connected to interface GE0/0.

(i) Construct a new entry for Figure 1 that would correctly route traffic to this new server farm. [2]

(ii) The network administrator is considering replacing all static routes with dynamic routing protocols. Discuss the advantages and disadvantages of using dynamic routing compared to static routing for OmniCorp's network, considering factors such as network size, complexity, and security. [6]